Potential speed-up for NUTS #1020
Description
Debugging NUTS with @jsalvatier yesterday we noticed that the computation of the energy E0 in NUTS, can be moved outside of the leapfrog loop: f332b1c to yield a potential speed-up. Unfortunately the code isn't quite working because of an issue with the logp function that requires a dict input rather than the array. It's probably easy to fix. I'll leave this here in case someone wants to pick it up.